打印二叉树结构 问题描述： 按凹入表形式横向打印二叉树结构，即二叉树的根在屏幕的最左边，二叉树的左子树在屏幕的下边，二叉树的右子树在屏幕的上边。 -Print binary tree structure to describe the problem: According to the form of horizontal indentation print binary tree structure, that is the root of binary tree on the s